Kids of the age these will be adamant just for few reasons like eating and also they will not offer toys while playing with others.
Also they will set in mind that being a kid if they cry parents will do anything for them.
But When the kid is adamant, we should make sure that we are not punishing them like beating. By punishing them will aggravate their feeling and will not make them to understand.
We should be patient enough to hold the kid and at first say that this is wrong; if he/she is continuing with this act then the other kids will deject him/her and will not play with him.
Any kid will not accept to these pleasing words, so we can divert them by offering the things which they like the most. Suppose if the kid is not giving some ball to other kids then we can divert the kid by saying like 'ride this bicycle which you like the most, else I will offer this to someone'
In case of 3-4 year old kid we want to make him eating, rather than just scolding and feeding him, we can say like 'if you eat soon then we will go and play outside or I will get you some toys'. By saying like this kids will eat on their own rather than scolding and compelling them.
This may also work.